Black Skirt Tetra — GloFish
Gymnocorymbus ternetzi
A robust, long-lived tetra with the characteristic black anal fin shaped like a skirt that fades toward the tail — hence the common name. The tall, compressed body with black-silver gradient makes it instantly recognizable. One of the most beginner-friendly tetras: tolerant, active and with a 3–5 year life expectancy. In schools of 6+ the fin-nipping tendency decreases drastically. Available in selected variants (long-fin) and unfortunately also in artificially dyed variants — the latter to be avoided for ethical and health reasons. Breeding moderately easy with a dedicated tank.
Wassertemperatur
22 - 26 °C
pH-Wert
6 - 7.5
Wassertyp
Süßwasser
Tankfüllstand
Mitte
Erwachsenengröße
6 cm
Mindesttankvolumen
>= 60 L
Mindestgruppe
>= 6
GH
3 - 15 dGH
KH
1 - 7 dKH
TDS
55 - 295 ppm
Leitfähigkeit
86 - 461 uS/cm
Artbeschreibung
Geographical Origin and Habitat: Does not exist in nature. The GloFish Tetra is a genetically modified organism (GMO) created in the laboratory by inserting fluorescent genes derived from jellyfish (for green) or corals (for red) into the genome of the wild Gymnocorymbus ternetzi.
Taxonomy and Morphology: Fluorescent Tetra (GloFish Tetra). The morphology is identical to that of the Black Skirt Tetra: high and rhomboidal body, very extensive anal fin. However, due to severe inbreeding in commercial farms, they are often slightly smaller (max 6 cm / 2.3 inches) and deformed.
Social Behavior: Maintains the gregarious and extremely hyperactive nature of the wild ancestor. Must be kept in dense schools (minimum 6-8 specimens). Unfortunately, if kept in tanks that are too small, they show severe intraspecific aggression and bite the fins of others.
Coloration and Sexual Dimorphism: Shocking. The colors (Starfire Red, Electric Green, Sunburst Orange, Cosmic Blue, Galactic Purple) are intrinsic, not injected, and are passed down genetically. They stand out blindingly under actinic blue LED lights. Females are larger and rounder.
Pflege, Zucht und Mitbewohner
Aquarium Setup: Despite their "toy" appearance, they need a REAL aquarium of at least 80 cm (32 inches). Commercial "GloFish kits" (10-liter spheres) are death traps. Free space in the center for frantic swimming. Lid mandatory.
Diet and Feeding: Very voracious and omnivorous. They instantly devour any flake or granular feed. To keep their immune system healthy (often compromised by inbreeding), regularly supplement with frozen bloodworms and brine shrimp.
Water Quality: They inherit the robustness of the wild Tetra, but not its longevity. They tolerate pH 6.0-7.5, GH 3-15 and temperatures of 22-26°C (71-79°F). They react very badly to nitrite and ammonia spikes, frequent in the small children's aquariums where they are often relegated.
Compatibility and Cohabitation: Perfect companions for Corydoras or peaceful bottom fish. NEVER pair them with slow fish with long fins (Betta Splendens, male Guppies), as they are unstoppable "fin-nippers" and would leave them finless in a few days.
Aquarium Breeding: They scatter eggs among the plants. They breed as easily as the wild form, generating fry that are already fluorescent. LEGAL NOTE: in many countries (including Europe) the sale, possession and breeding of these GMOs is strictly illegal.
Risks and Diseases: Ethically controversial fish. They chronically suffer from spinal malformations, tumors, early blindness and have a much shorter life expectancy (1-2 years) compared to the wild strain (5+ years), due to the lack of genetic diversity in the breeding farms.
Geografische Herkunft und Verbreitung
Does not exist in nature. The GloFish Tetra is a genetically modified organism (GMO) created in the laboratory by inserting fluorescent genes derived from jellyfish (for green) or corals (for red) into the genome of the wild Gymnocorymbus ternetzi.
Ursprung
Extra-Amazonas-SüdamerikaNordamerika
Fischprofil
- Temperament
- Semi-aggressive
- They are considered a schooling fish with a somewhat boisterous and lively temperament. While generally peaceful towards other species, they establish a pecking order within their own school through harmless chasing and displaying. If kept in too small of a group, they can become nervous or turn their nippy behavior towards other tank mates. When housed properly in a group of at least six to eight, they are active, entertaining, and relatively peaceful additions to a community setup.
- Diät
- Omnivore
- In their natural habitat, they are omnivores, feeding on a variety of small invertebrates, crustaceans, and plant matter. In captivity, they are unfussy eaters and will readily accept a staple diet of high-quality flake or pellet food. To ensure optimal health and vibrant coloration, their diet should be supplemented with live or frozen foods such as bloodworms, daphnia, and brine shrimp. They also benefit from occasional vegetable matter, which can be provided through specialized herbivore flakes or blanched vegetables.
- Lebenserwartung
- 3-5 years
- Erwachsenengröße
- 6 cm
- Geschlechterverhältnis
- School
- While they do not have a strict sex ratio requirement for general keeping, it is often best to keep a mix of males and females in a school. Males are typically slightly smaller and more slender than the plumper, deeper-bodied females. Keeping a slightly higher number of females to males can help diffuse any potential breeding-related chasing or harassment. However, in a sufficiently large school of six or more, a random mix usually works perfectly fine.
- Fütterungsfrequenz
- Twice daily
- Adult Black Skirt Tetras should typically be fed once or twice a day with small portions. It is crucial to only provide an amount of food they can completely consume within two to three minutes to prevent overfeeding. If you notice uneaten food settling on the substrate, you are likely feeding them too much. Fasting them for one day a week can also help clear their digestive tract and maintain water quality.
- Bioload
- Low to Medium
- Gymnocorymbus ternetzi produces a relatively moderate bioload for a tetra, especially considering their slightly larger and deeper body shape compared to neon tetras. While they are not overly messy, maintaining a group can collectively add significant waste to the aquarium. Therefore, adequate filtration and regular water changes are necessary to keep nitrate levels in check. A well-established nitrogen cycle is essential to handle their output effectively.
- Fluss
- Stagnant
- Coming from the slow-moving rivers, streams, and tributaries of South America, they prefer a gentle to moderate water flow. While they can swim quite actively, strong currents can exhaust them and cause unnecessary stress over time. Providing areas of still water, perhaps buffered by driftwood or dense planting, allows them to rest comfortably. Sponge filters or canister filters with a spray bar attachment are excellent choices to distribute the flow evenly.
- Sprungrisiko
- Yes
- Black Skirt Tetras are moderately active swimmers and have the potential to jump out of the aquarium, especially when startled. Sudden changes in lighting, aggressive tank mates, or poor water conditions can trigger their flight response. It is strongly advised to maintain a secure and well-fitting lid or cover glass on the aquarium at all times. Floating plants can also help make them feel more secure and deter them from attempting to jump.
- Reproduktion
- Oviparous
- They are egg-scatterers that provide no parental care and will readily consume their own eggs if given the chance. To successfully breed them, a separate breeding tank with very soft, slightly acidic water and dim lighting is required. The breeding tank should be equipped with fine-leaved plants or a spawning mop to catch the adhesive eggs. Once spawning has occurred, the adult fish must be immediately removed to protect the eggs, which typically hatch within 24 to 36 hours.
- Kompatibilität & Tankkameraden
- With caution
- This species is generally peaceful but can exhibit mild fin-nipping behavior, particularly if not kept in a large enough school. They are best kept with other robust, fast-moving fish of similar size, such as larger rasboras, barbs, and bottom-dwelling catfish. It is highly recommended to avoid keeping them with slow-moving or long-finned tank mates like bettas or angelfish, as these will likely be targeted. A large school of at least six individuals helps distribute any intra-species aggression and minimizes their interest in other species.
- Tankfüllstand
- Middle
- Black Skirt Tetras are primarily mid-water to top-water swimmers that utilize the open swimming spaces of the aquarium. They are very active and will frequently dart around the middle sections while looking for food or interacting with each other. Providing tall plants around the perimeter of the tank allows them plenty of unobstructed horizontal swimming room in the center. They will occasionally venture to the bottom to scavenge for dropped food, but spend the vast majority of their time higher up.
Wissenschaftliche Modelle & Parameter
FishBase
Zugang zu den offiziellen wissenschaftlichen Daten der Art
FishBase v25.04Daten synchronisiert am: 15.06.2026
- Trophäenniveau
- 3,1 ± 0,32 se
- Belastbarkeit
- Hoch (weniger als 15 Monate)
- Phylogenetische Einzigartigkeit (PD50)
- 0.5625
- Bayessche Längen-Gewichts-Beziehung
- a = 0.01995, b = 2.97
- AnfälligkeitGeringe Anfälligkeit (10 / 100)
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